rough idle, engine shake, max RPM 3000

MPScott1 · Mar 24, 2009

Hey if anybody can help me out i would appreciate it. I have a 1995 5.0L it has a rough idle, the engine shakes, and it won't go above 3000RPM. So far I've replaced all the spark plugs and wires, exhaust manifold gaskets, and the ignition control module.

whitegt94 · Mar 24, 2009

check your firing order

revhead347 · Mar 24, 2009

If the firing order is right, the distributer has gone bad. If you don't fix it, it will stop running altogether.

Kurt

MPScott1 · Mar 24, 2009

The distributor looks like it is still pretty new. Is there a way to check it?

divit250r · Mar 24, 2009

Check every vacuum hose and fitting for cracks. That can cause a serious rough idle.

Good luck!

MPScott1 · Mar 24, 2009

The firing order is correct. The only thing i noticed is that the distributor cap looks like it is turned to much compared to the picture in the haynes manual i have. Could that be an issue?

ProKiller · Mar 24, 2009

do you have a timing light to check your timing? is the distributor hold down bolt tight?

Dino Dino Bambino · Mar 24, 2009

MPScott1 said:
Hey if anybody can help me out i would appreciate it. I have a 1995 5.0L it has a rough idle, the engine shakes, and it won't go above 3000RPM. So far I've replaced all the spark plugs and wires, exhaust manifold gaskets, and the ignition control module.

Since you've just done some work on your ignition system:

1. Make sure you DO have the correct firing order. Remember that the distributor rotor turns counterclockwise, and the cylinders are numbered 1-4 on the passenger side and 5-8 on the driver's side.

View attachment 265083

2. Make sure you don't have any plug wires arcing on the header tubes. This will be more obvious if you have the hood open and the engine idling when it's dark outside.

3. Check the timing.

99FiveOh · Mar 24, 2009

Yeah, I'd almost bet money there are two wires crossed. My old boss used to use a test light to check it. He'd ground it out and push the test light into each plug wire boot on the top of the distributor. If the cylinder is firing, you'll hear it run differently when you push the test light in. If there's no change, that cylinder isn't firing and is probably crossed with another.

MPScott1 · Mar 25, 2009

Where do you check the timing at? I know you check it on the bottom pulley, but do you put the light on the hole on the passenger side of the pulley?

ProKiller · Mar 25, 2009

theres a bracket that is by the balancer by the crank pulley. as the numbers on the balancer go around they line up with the bracket, thats your timing then. do a search to learn more about changing your timing.

99FiveOh · Mar 25, 2009

I can't see timing causing this condition though. If it was extremely out of time, it wouldn't even start.

lees gt · Mar 25, 2009

I had the same problem,turned out to be blocked cats,unscrew 02 sensors to let it breath and see if its any better..

MPScott1 · Mar 26, 2009

lees gt said:
I had the same problem,turned out to be blocked cats,unscrew 02 sensors to let it breath and see if its any better..

Do that while it's running right?

Killercanary · Mar 26, 2009

I just bought a 94 cobra that was 100% stock with 154K miles. It idled fine, and rev'd nice and smooth until it got to 4000rpms and then it just stopped. It was way down on power and felt choked above 4000. I too had a clogged cat. My front passenger side cat had come apart and it was in pieces in front of the rear cat blocking that bank of the engine from being able to flow. I put an offroad X pipe that I had laying around on it and it completely fixed the problem. Did you have the H pipe off when you put the manifold gaskets on? Did you hear anything rattling in it?

I will add that it sounds like a timing issue to me though as others have stated.

MPScott1 · Mar 26, 2009

no i left the pipes on. I had just enough room to take the old gaskets off and put the new ones on. I haven't had a chance to check the timing yet, but the majority says that is probably the issue.

revhead347 · Mar 26, 2009

Killercanary said:
I just bought a 94 cobra that was 100% stock with 154K miles. It idled fine, and rev'd nice and smooth until it got to 4000rpms and then it just stopped. It was way down on power and felt choked above 4000. I too had a clogged cat. My front passenger side cat had come apart and it was in pieces in front of the rear cat blocking that bank of the engine from being able to flow. I put an offroad X pipe that I had laying around on it and it completely fixed the problem. Did you have the H pipe off when you put the manifold gaskets on? Did you hear anything rattling in it?

I will add that it sounds like a timing issue to me though as others have stated.

That happened to my car too. One of the front cats popped, and the crap went downstream and blocked the back too. Took me forever to figure out what was wrong with the car. It would run so hot you could cook a steak on the manifold.

Kurt

OrangeMustangGt · Mar 26, 2009

one more thing may be your MAF.... I had one go bad, but was still within the paramaters so it did not CEL, but was pegged at 5.0v. Unplug it and see if it runs better

MPScott1 · Mar 26, 2009

I unplugged the MAF and it ran worse.

MPScott1 · Apr 3, 2009

i checked the timing and it was fine, i still have to check the cats though.

rough idle, engine shake, max RPM 3000

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